The present invention relates to a system for controlling the sequential operation of a plurality of air control valves and more particularly finds application in controlling the functions of exhaust gas recirculation and idle speed bypass for an internal combustion engine as well as within an automotive three-way catalyst secondary air control system.
Modern automobile engines must usually be maintained at sufficiently low engine speeds in order to lessen the amount of pollutants given off by the engine while it is idling. The idle speed bypass valve (idle air bypass valve or bypass valve) is utilized to set the engine idle speed as a function of the load on the engine. As is known, when vehicle accessories are switched on with the engine in an idling condition, the engine may stall. An example of idle speed bypass valves is illustrated in U.S. Pat. No. 4,388,856 which illustrates a pneumatic device which controls the positioning of a plunger which in turn is used to vary the position of the throttle mechanism to readjust the engine idle speed as a function of engine load.
In order to reduce exhaust gas emissions when the engine is off-idle, an exhaust gas recirculation valve has typically has been used to recirculate a determinable percentage of the exhaust gas within an exhaust system of the engine into the intake manifold.
The controlling of engine idle speed and EGR recirculation conventionally utilized two separate and independent mechanisms to control these separate and independent functions. A modification of these earlier systems is shown by Yamaguchi in U.S. Pat. No. 4,281,631 which uses a single solenoid valve but still requires an electrically responsive changeover valve.
It is an object of the present invention to provide a system employing a single vacuum regulating device to selectively control the vacuum applied to a plurality of air control devices.
A further object of the present invention is to utilize a single vacuum regulating device to control the operation of an exhaust gas recirculation (EGR) valve and an idle speed bypass valve.
As can be seen from the discussion below the present invention has application to another type of exhaust control device which is conventionally referred to as a three-way catalyst secondary air control system. These systems classically utilize a dump valve for dumping the output of an air pump either to atmosphere or to another pneumatic valve commonly referred to as a switch valve which channels the air pump flow either mid-bed of the catalytic converter or to its entrance. The dump valve and switch valve have characteristically been controlled by separate solenoid switches in a manner having commonality with the control of the above-mentioned EGR-idle speed control systems. It is therefore a further object of the present invention to utilize a single vacuum regulating device to control the operation of a dump valve and a switch valve for application within a three-way catalyst secondary air control system.
It is a further object of the present invention to provide a system for combined control of the above-identified valves which exhibits simple construction and efficient operation.
Accordingly the invention comprises a flow control system responsive to fluid pressure comprising means for varying the magnitude of the pressure within a plurality of different pressure ranges; a plurality of pressure responsive valves communicated with said pressure means, each valve having at least two operative conditions and means for sequentially changing the operative condition of a particular one of the plurality of pressure responsive valves in response to changes in the magnitude of pressure communicated thereto.
Many other objects and purposes of the invention will be clear from the detailed description of the drawings.